A blizzard is a severe snowstorm characterized by strong sustained winds of at least 56 km/h (35 mph) and lasting for a prolonged period of time—typically three hours or more. A ground blizzard is a weather condition where snow is not falling but loose snow on the ground is lifted and blown by strong winds.

In the United States, the National Weather Service defines a blizzard as a severe snowstorm characterized by strong winds causing blowing snow that results in low visibilities. The difference between a blizzard and a snowstorm is the strength of the wind, not the amount of snow. To be a blizzard, a snow storm must have sustained winds or frequent gusts that are greater than or equal to 56 km/h (35 mph) with blowing or drifting snow which reduces visibility to 400 m or 0.25 mi or less and must last for a prolonged period of time—typically three hours or more.[1][2]

While severe cold and large amounts of drifting snow may accompany blizzards, they are not required. Blizzards can bring whiteout conditions, and can paralyze regions for days at a time, particularly where snowfall is unusual or rare.

A severe blizzard has winds over 72 km/h (45 mph), near zero visibility, and temperatures of −12 °C (10 °F) or lower.[3] In Antarctica, blizzards are associated with winds spilling over the edge of the ice plateau at an average velocity of 160 km/h (99 mph).[3]

Ground blizzard refers to a weather condition where loose snow or ice on the ground is lifted and blown by strong winds. The primary difference between a ground blizzard as opposed to a regular blizzard is that in a ground blizzard no precipitation is produced at the time, but rather all the precipitation is already present in the form of snow or ice at the surface.

The Australia Bureau of Meteorology describes a blizzard as, "Violent and very cold wind which is laden with snow, some part, at least, of which has been raised from snow covered ground." [4]

Blizzard conditions of cold temperatures and strong winds can cause wind chill values that can result in hypothermia or frostbite. The wind chill factor is the amount of cooling the human body feels due to the combination of wind and temperature.

Blizzards are not common in mainland Australia, but occur frequently in the Snowy Mountains in New South Wales and Victoria. When blizzards do occur, they can affect the Tasmanian Highlands and, particularly, Mount Wellington, which towers over the Tasmanian capital Hobart. Blizzards do not affect any major towns or cities, because there are no populated areas located in the mountains except for the ski resort towns of New South Wales and Victoria.

March blizzard in North Dakota, 1966. Caption jokingly reads "I believe there is a train under here somewhere!"

In the United States, storm systems powerful enough to cause blizzards usually form when the jet stream dips far to the south, allowing cold, dry polar air from the north to clash with warm, humid air moving up from the south.[2][5] They are most common in the Great Plains, the Great Lakes states, and the northeastern states along the coast, and less common in the Pacific Northwest.

Another storm system occurs when a cold core low over the Hudson Bay area in Canada is displaced southward over southeastern Canada, the Great Lakes, and New England. When the rapidly moving cold front collides with warmer air coming north from the Gulf of Mexico, strong surface winds, significant cold air advection, and extensive wintry precipitation occur.

Conditions approaching a blizzard whiteout in Minnesota, on March 1, 2007. Note the unclear horizon near the center.

Low pressure systems moving out of the Rocky Mountains onto the Great Plains, a broad expanse of flat land, much of it covered in prairie, steppe and grassland, can cause thunderstorms and rain to the south and heavy snows and strong winds to the north. With few trees or other obstructions to reduce wind and blowing, this part of the country is particularly vulnerable to blizzards with very low temperatures and whiteout conditions. In a true whiteout there is no visible horizon. People can become lost in their own front yards, when the door is only 3 m (10 ft) away, and they would have to feel their way back. Motorists have to stop their cars where they are, as the road is impossible to see.

A nor'easter is a macro-scale storm along the East Coast of the United States and Atlantic Canada; it gets its name from the direction the wind is coming from. The usage of the term in North America comes from the wind associated with many different types of storms some of which can form in the North Atlantic Ocean and some of which form as far south as the Gulf of Mexico. The term is most often used in the coastal areas of New England and Atlantic Canada. This type of storm has characteristics similar to a hurricane. More specifically it describes a low-pressure area whose center of rotation is just off the East Coast and whose leading winds in the left-forward quadrant rotate onto land from the northeast. High storm waves may sink ships at sea and cause coastal flooding and beach erosion. Notable nor'easters include The Great Blizzard of 1888, one of the worst blizzards in U.S. history. It dropped 100–130 cm (40–50 in) of snow and had sustained winds of more than 45 miles per hour (72 km/h) that produced snowdrifts in excess of 50 feet (15 m). Railroads were shut down and people were confined to their houses for up to a week. It killed 400 people, mostly in New York.

The 1972 Iran Blizzard, which caused approximately 4,000 deaths, was the deadliest blizzard in recorded history. Dropping as much as 26 feet (7.9 m) of snow, it completely covered 200 villages. After a snowfall lasting nearly a week, an area the size of Wisconsin was entirely buried in snow.[6]

A snow blockade in southern Minnesota. On March 29, 1881, snowdrifts in Minnesota were higher than locomotives.

The winter of 1880–1881 is widely considered the most severe winter ever known in the United States. Many children—and their parents—learned of "The Snow Winter" through the children's book The Long Winter by Laura Ingalls Wilder, in which the author tells of her family's efforts to survive. The snow arrived in October 1880 and blizzard followed blizzard throughout the winter and into March 1881, leaving many areas snowbound throughout the entire winter. Accurate details in Wilder's novel include the blizzards' frequency and the deep cold, the Chicago and North Western Railway stopping trains until the spring thaw because the snow made the tracks impassable, the near-starvation of the townspeople, and the courage of her future husband Almanzo and another man, who ventured out on the open prairie in search of a cache of wheat that no one was even sure existed.

The October blizzard brought snowfalls so deep that two-story homes had snow up to the second floor windows. No one was prepared for the deep snow so early in the season and farmers all over the region were caught before their crops had even been harvested, their grain milled, or with their fuel supplies for the winter in place. By January the train service was almost entirely suspended from the region. Railroads hired scores of men to dig out the tracks but it was a wasted effort: As soon as they had finished shoveling a stretch of line, a new storm arrived, filling up the line and leaving their work useless.

There were no winter thaws and on February 2, 1881, a second massive blizzard struck that lasted for nine days. In the towns the streets were filled with solid drifts to the tops of the buildings and tunneling was needed to secure passage about town. Homes and barns were completely covered, compelling farmers to tunnel to reach and feed their stock.

When the snow finally melted in late spring of 1881, huge sections of the plains were flooded. Massive ice jams clogged the Missouri River and when they broke the downstream areas were ravaged. Most of the town of Yankton, in what is now South Dakota, was washed away when the river overflowed its banks.[7][8]

The Storm of the Century, also known as the Great Blizzard of 1993, was a large cyclonic storm that formed over the Gulf of Mexico on March 12, 1993, and dissipated in the North Atlantic Ocean on March 15. It is unique for its intensity, massive size and wide-reaching effect. At its height, the storm stretched from Canada towards Central America, but its main impact was on the Eastern United States and Cuba. The cyclone moved through the Gulf of Mexico, and then through the Eastern United States before moving into Canada. Areas as far south as central Alabama and Georgia received 15 to 20 cm (6 to 8 in) of snow and areas such as Birmingham, Alabama, received up to 30 cm (12 in) with isolated reports of 41 cm (16 in). Even the Florida Panhandle reported up to 10 cm (4 in),[9] with hurricane-force wind gusts and record low barometric pressures. Between Louisiana and Cuba, hurricane-force winds produced high storm surges across northwestern Florida, which along with scattered tornadoes killed dozens of people. Record cold temperatures were seen across portions of the South and East in the wake of this storm. In the United States, the storm was responsible for the loss of electric power to over 10 million customers. It is purported to have been directly experienced by nearly 40 percent of the country's population at that time. A total of 310 people, including 10 from Cuba, perished during this storm.

Schoolhouse Blizzard of 1888, North American Great Plains. January 12–13, 1888. What made the storm so deadly was the timing (during work and school hours), the suddenness, and the brief spell of warmer weather that preceded it. In addition, the very strong wind fields behind the cold front and the powdery nature of the snow reduced visibilities on the open plains to zero. People ventured from the safety of their homes to do chores, go to town, attend school, or simply enjoy the relative warmth of the day. As a result, thousands of people—including many schoolchildren—got caught in the blizzard.

Great Blizzard of 1888 March 11–13, 1888. One of the most severe recorded blizzards in the history of the United States. On March 12, an unexpected northeaster hit New England and the mid-Atlantic, dropping up to 130 cm (50 in) of snow in the space of two days. Some 400 people died, including many sailors aboard vessels that were beset by gale-force winds and turbulent seas. In parts of New York City, snowdrifts reached up to the second story of some buildings.

Great Blizzard of 1899 February 11–14, 1899. An extremely unusual blizzard in that it reached into the far southern states of America. It hit in February, and the area around Washington, D.C., experienced 51 hours straight of snowfall. The port of New Orleans was totally iced over; revelers participating in the New Orleans Mardi Gras had to wait for the parade routes to be shoveled free of snow. Concurrent with this blizzard was the extremely cold arctic air. Many city and state record low temperatures date back to this event, including all-time records for locations in the Midwest and South. State record lows: Nebraska reached −47 °F (−44 °C), Ohio experienced −39 °F (−39 °C), Louisiana bottomed out at −16 °F (−27 °C), and Florida dipped below zero to −2 °F (−19 °C).

Armistice Day Blizzard November 10–12, 1940. Took place in the Midwest region of the United States on Armistice Day. This "Panhandle hook" winter storm cut a 1,600-kilometre-wide path (1,000 mi) through the middle of the country from Kansas to Michigan. The morning of the storm was unseasonably warm but by mid afternoon conditions quickly deteriorated into a raging blizzard that would last into the next day. A total of 145 deaths were blamed on the storm, almost a third of them duck hunters who had taken time off to take advantage of the ideal hunting conditions. Weather forecasters had not predicted the severity of the oncoming storm, and as a result the hunters were not dressed for cold weather. When the storm began many hunters took shelter on small islands in the Mississippi River, and the 80 km/h (50 mph) winds and 1.5-metre (5 ft) waves overcame their encampments. Some became stranded on the islands and then froze to death in the single-digit temperatures that moved in over night. Others tried to make it to shore and drowned.

North American blizzard of 1947 December 25–26, 1947. Was a record-breaking snowfall that began on Christmas Day and brought the Northeast United States to a standstill. It was not accompanied by high winds, but the snow fell steadily with drifts reaching 3.0 m (10 ft). Seventy-seven deaths were attributed to the blizzard.

Great Blizzard of 1978 also called the Cleveland Superbomb. January 25–27, 1978. Was one of the worst snowstorms the Midwest has ever seen. Wind gusts approached 160 km/h (100 mph), causing snowdrifts to reach heights of 7.6 m (25 ft) in some areas, making roadways impassable.

1993 Storm of the Century March 12–15, 1993. While the southern and eastern U.S. and Cuba received the brunt of this massive blizzard, the Storm of the Century impacted a wider area than any in recorded history.